Like many other terms, the technical definition of bandwidth is somewhat different from its use in reference to web sites and data transfer. For our purposes, and yours, bandwidth refers to the amount of data that can be transferred from your web site to the world.
When shopping for a web site hosting plan, we often ask. "How many hits can I get? How many visitors will my site be able to handle?" The response is always the same. "That depends."
There is a great deal of confusion as to how exactly your web pages are distributed and what the practical limits of that distribution are. Before we discuss "bandwidth", let's discuss the bits and pieces of web site hosting.
In order to have a web site you need the following things:
1. An address - These are stored on large Domain Name Servers that, much like a phone book, points visitors requesting your site name to the computer that distributes the pages of your site.
2. A computer - The physical machine where your site's pages and images are stored. This is referred to as the server since it serves data (your web pages) based on client (visitor) requests.
3. A connection - A data line connecting your server to the global network - the Internet. Technically it is possible to serve web sites from any web connection, including a dial-up modem, but this of course is slow and inefficient. Faster lines like T-1's (1.5 MB/Sec.), T-3's (44.7 MB/Sec.) and clusters of fiber optic T-3 lines called Optical Carriers (OC's) are more appropriate. Since fast connections are often too expensive for smaller companies and individual web site owners, hosting companies play a role in serving large numbers of website owners in one data facility with very fast (and expensive) data line connections. Simply, the primary purpose of having a web host is tapping into fast data line connections whose cost is spread over thousands (or hundreds of thousands) of web sites.
In order to further reduce the cost of web hosting, companies also offer shared hosting, which means the server houses not only your web site, but many others. These are often regular computers - nothing fancy- with large hard drives and one or two 100 MB/sec. network cards. Consider that at 100 MB per client, a 20 GB hard drive could hold 150 web sites. At $25 per month, one server could generate $60,000 of income for a web site host per year. Of course, the facility, support, back-ups, networking equipment and the data lines eat up a good portion of that money. A T-3 can cost anywhere from $10,000-40,000 (prices are dropping) per month and most web hosts will use clusters of these. Primarily you are paying for the fast pipeline to the Internet.
Okay, so what does this all mean?
Let's assume that your home page, the first page served to your visitors, has a file size of 50 KB, 15 KB for the actual HTML page and 35 KB for images included on that page - backgrounds, buttons, logo, photos, etc.. Lets also assume that your site gets 10,000 visitors per month and the average visitor views 3 pages of your site, also 50 KB each.
Based on those numbers, your site would serve: 50 KB x 3 Pages x 10,000 Visitors = 1500000 KB or 1500 MB or 1.5 GB per month.
Let's look at your data transfer based on server load. Assuming this traffic was evenly distributed, your server would be distributing 1.5 GB per month <insert long math equation here> or about 6 KB per second. At this rate your server is barely working. Let's assume that all of you visitors come to your site during the same hour of every day. Even then, the server load during this hour would only be 833 KB per second or less than 1 MB.
The Bottom Line
There are a number of limiting factors that can interfere with web site performance, the least of which is the capability of the data line. The number of other sites hosted on the server, the type of applications those sites (and yours) are running such as CGI scripts and database applications, the server hardware (processor speed, drive speed and memory) all contribute to the overall performance of your server.
When shopping for a web site hosting plan, we often ask. "How many hits can I get? How many visitors will my site be able to handle?" The response is always the same. "That depends."
There is a great deal of confusion as to how exactly your web pages are distributed and what the practical limits of that distribution are. Before we discuss "bandwidth", let's discuss the bits and pieces of web site hosting.
In order to have a web site you need the following things:
1. An address - These are stored on large Domain Name Servers that, much like a phone book, points visitors requesting your site name to the computer that distributes the pages of your site.
2. A computer - The physical machine where your site's pages and images are stored. This is referred to as the server since it serves data (your web pages) based on client (visitor) requests.
3. A connection - A data line connecting your server to the global network - the Internet. Technically it is possible to serve web sites from any web connection, including a dial-up modem, but this of course is slow and inefficient. Faster lines like T-1's (1.5 MB/Sec.), T-3's (44.7 MB/Sec.) and clusters of fiber optic T-3 lines called Optical Carriers (OC's) are more appropriate. Since fast connections are often too expensive for smaller companies and individual web site owners, hosting companies play a role in serving large numbers of website owners in one data facility with very fast (and expensive) data line connections. Simply, the primary purpose of having a web host is tapping into fast data line connections whose cost is spread over thousands (or hundreds of thousands) of web sites.
In order to further reduce the cost of web hosting, companies also offer shared hosting, which means the server houses not only your web site, but many others. These are often regular computers - nothing fancy- with large hard drives and one or two 100 MB/sec. network cards. Consider that at 100 MB per client, a 20 GB hard drive could hold 150 web sites. At $25 per month, one server could generate $60,000 of income for a web site host per year. Of course, the facility, support, back-ups, networking equipment and the data lines eat up a good portion of that money. A T-3 can cost anywhere from $10,000-40,000 (prices are dropping) per month and most web hosts will use clusters of these. Primarily you are paying for the fast pipeline to the Internet.
Okay, so what does this all mean?
Let's assume that your home page, the first page served to your visitors, has a file size of 50 KB, 15 KB for the actual HTML page and 35 KB for images included on that page - backgrounds, buttons, logo, photos, etc.. Lets also assume that your site gets 10,000 visitors per month and the average visitor views 3 pages of your site, also 50 KB each.
Based on those numbers, your site would serve: 50 KB x 3 Pages x 10,000 Visitors = 1500000 KB or 1500 MB or 1.5 GB per month.
Let's look at your data transfer based on server load. Assuming this traffic was evenly distributed, your server would be distributing 1.5 GB per month <insert long math equation here> or about 6 KB per second. At this rate your server is barely working. Let's assume that all of you visitors come to your site during the same hour of every day. Even then, the server load during this hour would only be 833 KB per second or less than 1 MB.
The Bottom Line
There are a number of limiting factors that can interfere with web site performance, the least of which is the capability of the data line. The number of other sites hosted on the server, the type of applications those sites (and yours) are running such as CGI scripts and database applications, the server hardware (processor speed, drive speed and memory) all contribute to the overall performance of your server.
